1. Field of the Invention
The present invention relates to a transmission for a vehicle such as a motorcycle that is occasionally pushed under human power, and particularly to an improvement in a connection between an engine crankshaft and a wheel drive shaft through a static hydraulic infinitely variable transmission.
2. Background Art
In a transmission of the related art, a centrifugal type starting clutch is interposed between the engine crankshaft and a static hydraulic infinitely variable transmission. As disclosed in Japanese Patent Laid-open No. Hei. 11-115870, when the engine in this arrangement is idling or operation is suspended, the starting clutch is disengaged so that the vehicle can be pushed under human power without engine resistance.
In the above described related art, when the vehicle is pushed under human power when the engine is idling or operation is suspended, a transmission system reaching from a wheel to the centrifugal clutch is rotated. However, since there is a comparatively heavy static hydraulic infinitely variable transmission system included in the transmission, when the vehicle is pushed a large force is required to overcome the large inertial resistance of the static hydraulic infinitely variable transmission and frictional resistance of respective parts.
The present invention overcomes the shortcomings associated with the related art and achieves other advantages not realized by the prior art.
An object of the present invention is to solve the above-described problems of conventional vehicle transmissions and to provide a vehicle transmission that can be lightly pushed without being affected by the inertial resistance of the static hydraulic infinitely variable transmission when the engine is idling or operation is suspended.
These and other objects are accomplished by a vehicle transmission for operatively connecting to a crankshaft of an engine and a vehicle wheel drive shaft, said transmission comprising a static hydraulic infinitely variable transmission including a connection for connecting said transmission to said crankshaft and a connection for connecting said transmission to said vehicle wheel drive shaft a hydraulic pump extending to an engine side of said transmission a hydraulic motor extending to a wheel drive shaft side of said transmission, wherein said pump and said motor are connected together using a closed hydraulic circuit, and a control clutch arranged in said transmission on said wheel drive shaft side between said hydraulic motor and said connection for said wheel drive shaft, wherein said control clutch is disengaged if said engine is idling and when operation of said engine is suspended.
According to this first aspect, by disengaging the control clutch when the engine is idling or operation is suspended, it is possible to disconnect inverse load from the vehicle wheels to the static hydraulic infinitely variable transmission. Accordingly, in the event that the vehicle is pushed along under the power of just the rider, the vehicle can be relatively lightly operated without being affected by the large inertial resistance of the static hydraulic infinitely variable transmission.
In a second aspect of the present invention, in addition to the first aspect, the control clutch is a hydraulic type that engages using hydraulic pressure derived from an supply oilway connecting between an supply pump driven by the engine and the static hydraulic infinitely variable transmission.
According to this second aspect, by setting the introduction hydraulic pressure to the control clutch it is possible to allow a desired friction bonding force in the clutch, which contributes to reduction in size of the clutch. Furthermore, hydraulic pressure introduced to the control clutch is derived from a supply oilway of the static hydraulic infinitely variable transmission which means that there is no need for a dedicated control clutch oil pump, making it possible to keep cost increases as low as possible.
A third aspect of the present invention, in addition to the second aspect, has an electromagnetic control valve for controlling hydraulic pressure supply to the control clutch fitted in oilways connecting between the supply oilway and the control clutch.
According to the third aspect, the electromagnetic control valve is controlled so as to disconnect or weaken introduction pressure to the hydraulic chamber according to operating conditions of the engine, making it possible to carry out transmission control according to various operating conditions.
These and other objects are accomplished by a static hydraulic infinitely variable vehicle transmission for operatively connecting to a crankshaft of an engine and a vehicle wheel drive shaft, said transmission comprising a connection for connecting said transmission to said crankshaft and a connection for connecting said transmission to said vehicle wheel drive shaft; a hydraulic pump extending to an engine side of said transmission; a hydraulic motor extending to a wheel drive shaft side of said transmission, wherein said pump and said motor are connected together using a closed hydraulic circuit; a control clutch arranged in said transmission on said wheel drive shaft side between said hydraulic motor and said connection for said wheel drive shaft, wherein said control clutch is disengaged if said engine is idling and when operation of said engine is suspended; and a cylinder block rotatably driven according to a sum of reaction torque received from said hydraulic pump and a reaction torque received from said hydraulic motor, wherein said sum is a rotational torque capable of being transmitted through said control clutch to said wheel drive shaft connection.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.